A SYNOPTICAL ACCOUNT OF THE STERCULIACEAE IN BANGLADESH

Taxonomy, updated nomenclature and occurrence of the species belonging to the family Sterculiaceae in Bangladesh have been presented. Detailed herbarium study at Royal Botanic Gardens, Kew (K), Royal Botanic Garden, Edinburgh (E), British Museum (BM), Bangladesh National Herbarium (DACB) and Dhaka University Salar Khan Herbarium (DUSH) has revealed the occurrence of 32 species under 15 genera of the Sterculiaceae in Bangladesh. The correct name, important synonym(s), salient diagnostic characteristics, specimens examined and distributional notes have been provided for each species. Dichotomous bracketed keys have also been presented for identification of genera and species. Introduction The Sterculiaceae is a family of tropical and sub-tropical plants, comprising nearly 70 genera and 1,500 species (Cronquist, 1981). They are characterized by the presence of stellate hairs, bilocular anthers, 10 to numerous stamens in two or more whorls, mostly connate by their filaments, superior ovary, anatropous ovules and axile placentation. The family consists of softwooded trees and shrubs, and a few herbaceous and climbing species. Many species growing in rain forests are remarkable for their development of plank buttresses. Systematically it is placed in the Malvales by Engler and Prantle (1896), and shows many features in common with the other families of that group, namely Tiliaceae, Elaeocarpaceae, Bombacaceae and Malvaceae. Evidence from floral anatomy and embryology suggests that the Sterculiaceae is the most primitive in the Malvales (Brizicky, 1966). Hooker (1874) recognized six tribes of the Sterculiaceae, viz., Sterculieae, Helictereae, Eriolaeneae, Dombeyeae, Hermannieae and Buettnerieae (Byttnerieae). Based on floral anatomy and embryology the tribe Sterculieae is regarded as the most primitive because of the presence of pentacyclic flowers, numerous stamens, apocarpous gynoecia, and many ovulate locules, while the Hermannieae is the most advanced tribe as it possesses tetracyclic flowers, a reduced number of stamens and ovules, and a tendency of perigyny. In respect to perianth structure, the Helictereae and Byttnerieae appear to be the most highly specialized tribes of Sterculiaceae (Brizicky, 1966). Several taxonomic treatments on the Sterculiaceae have been made based on morphology (Robyns and Cautrecasas, 1964; Hsiang-Hao, 1984; Malick, 1993; Verdcourt, 1995; Phengklai, 2001). Hooker (1874) worked out the Sterculiaceous taxa of British India, while Prain (1903) dealt with the species of the then Bengal documenting 20 species and 9 species, respectively from the area of present Bangladesh. Despite Khan (1972-1989), and Khan and Rahman (1989-2002) published the Flora of Bangladesh in different fascicles covering several angiospermic families, the Sterculiaceae was not included in those treatments. Ahmed et al. (2009) listed 25 species of 1 Corresponding author. Email: dr_oliur@yahoo.com 2 Former Principal Scientific Officer, Bangladesh National Herbarium, Mirpur 1, Dhaka 1216, Bangladesh. 3 Former Consultant-Taxonomist, University of Illinois at Chicago, USA.


Introduction
The Sterculiaceae is a family of tropical and sub-tropical plants, comprising nearly 70 genera and 1,500 species (Cronquist, 1981).They are characterized by the presence of stellate hairs, bilocular anthers, 10 to numerous stamens in two or more whorls, mostly connate by their filaments, superior ovary, anatropous ovules and axile placentation.The family consists of softwooded trees and shrubs, and a few herbaceous and climbing species.Many species growing in rain forests are remarkable for their development of plank buttresses.Systematically it is placed in the Malvales by Engler and Prantle (1896), and shows many features in common with the other families of that group, namely Tiliaceae, Elaeocarpaceae, Bombacaceae and Malvaceae.Evidence from floral anatomy and embryology suggests that the Sterculiaceae is the most primitive in the Malvales (Brizicky, 1966).Hooker (1874) recognized six tribes of the Sterculiaceae, viz., Sterculieae, Helictereae, Eriolaeneae, Dombeyeae, Hermannieae and Buettnerieae (Byttnerieae).Based on floral anatomy and embryology the tribe Sterculieae is regarded as the most primitive because of the presence of pentacyclic flowers, numerous stamens, apocarpous gynoecia, and many ovulate locules, while the Hermannieae is the most advanced tribe as it possesses tetracyclic flowers, a reduced number of stamens and ovules, and a tendency of perigyny.In respect to perianth structure, the Helictereae and Byttnerieae appear to be the most highly specialized tribes of Sterculiaceae (Brizicky, 1966).
Several taxonomic treatments on the Sterculiaceae have been made based on morphology (Robyns and Cautrecasas, 1964;Hsiang-Hao, 1984;Malick, 1993;Verdcourt, 1995;Phengklai, 2001).Hooker (1874) worked out the Sterculiaceous taxa of British India, while Prain (1903) dealt with the species of the then Bengal documenting 20 species and 9 species, respectively from the area of present Bangladesh.Despite Khan (1972Khan ( -1989)), and Khan andRahman (1989-2002) published the Flora of Bangladesh in different fascicles covering several angiospermic families, the Sterculiaceae was not included in those treatments.Ahmed et al. (2009) listed 25 species of Sterculiaceae under 13 genera from Bangladesh.Very recently Mia et al. (2011) reported three species of Sterculiaceae, namely Guazuma ulmifolia Lam., Helicteres viscida Bl. and Sterculia urens Roxb.as new distributional records for Bangladesh.However, no detailed study was carried out on this family so far.Moreover, plants of Bangladesh belonging to this family deposited in different foreign herbaria, particularly Royal Botanic Gardens, Kew (K), Royal Botanic Garden, Edinburgh (E) and British Museum (BM) have never been investigated earlier.The present study aimed at studying all species of Sterculiaceae of Bangladesh deposited in the herbaria both at home and abroad, and documenting and detailing all members of the family occurring in Bangladesh along with their updated nomenclatural and distributional notes.

Materials and Methods
The present study is based on both literature survey and herbarium studies.Plants deposited at K, E, BM, Bangladesh National Herbarium (DACB) and Dhaka University Salar Khan herbarium (DUSH) have been examined critically.Dichotomous artificial keys have been provided for identification of genera and species.Nomenclature has been updated for each species along with their important synonyms following Verdcourt (1995), Phengklai (2001) and Ahmed et al. (2009).Salient diagnostic characters, specimens examined and distributional notes have also been furnished under each species.

Results
The present study revealed the occurrence of 32 species under 15 genera of the family Sterculiaceae in Bangladesh.A dichotomous artificial key to genera of the Sterculiaceae is given below.

Key to the genera:
1.

Dombeya mastersii
A medium-sized spreading, deciduous tree with fluted stem.Leaves crowded at the end of branchlets, palmately 3-5 lobed, lobes triangular, with acute to cuspidate apex and cordate to truncate base.Flowers scarlet or orange-red, polygamous.Fruit a follicle, oblong.Flowering and fruiting: March-June.
Note: Malick (1993) reported the occurrence of this species from Bangladesh without citing any specific locality.Although Ahmed et al. (2009) cited this species from Bangladesh, however no specimen belonging to this species was available for citation.Distribution: Australia, Cambodia, China, India, Indonesia, Malaysia, Nepal, Pakistan, Sri Lanka, Thailand and Vietnam.

Maurit.: 35 (1837).
A shrub with stellate hairs on all parts.Leaves ovate-oblong to lanceolate with cuspidate apex and auriculate or cordate base.Flowers white or yellow.Fruit a capsule, oblong or cylindrical, beaked, covered with shaggy hairs.Flowering and fruiting: July-March.
Distribution: India, Myanmar and Thailand.
A small to medium-sized evergreen tree.Leaves ovate to oblong, with acute apex and obtuse to subtruncate base.Male flowers with 8-10 stamens.Female flowers with 4-5 carpels.Fruit a samara, ellipsoid, woody with a longitudinal ridge, epicarp shining.Flowering and fruiting: May-December.
Annual herb to undershrub with few scattered stellate hairs on the bark.Leaves linear lanceolate, with acuminate or cuspidate apex and cuneate or obtuse base.Flowers pink to red.Fruit a globose or subglobose capsule, 5-valved.Flowering and fruiting: September-January.

Key to the species:
1.